Just my observations, not so much a critique/demand/request/etc.
I recently bought an appletv and got xbmc on it, so I only have a couple weeks experience with it.
I've tried the latest transparency (2.01 as I recall), and observed some of the same behavior mentioned in the 1st post of topic.
In particular, I was trying to use the movie slide mode, but the horizontal scrolling was pretty slow and even still alot of times (the dvd cover) images would not be loaded as they scroll past. I realize that the fanart normally pops in the background when you pause on a movie, but the same thing happened with the dvd covers, typically only showing up when you stop.
I don't know if its a cache/memory issue or cpu processing, but I have ~650 movies listed when no filtering and it only takes a dozen or movies worth of scrolling for it to get behind.
Also as a side note, in slide mode when you move to the scrollbar under the movie slide, it still only moves 1 movie at a time instead of the expected page at a time. And the plot window did not seem sized right (xbmc and atv set for 720p full screen).
I was going to, and still intend to, try the xbox version, I just haven't taken the time.
Great skin tho, I really like it.